Method and apparatus for coating a pipe



July 23, 1968 J. D. M CUNE METHOD AND APPARATUS FOR COATING A PIPE Filed June 15, 1964 (/OWEJ 0. Maia/7e INVENTOR. {M I ATTORNEY United States Patent 3,394,025 METHOD AND APPARATUS FOR COATING A PIPE James D. Mc-Cnne, La Porte, Tex., assignor, by mesne assignments, to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed June 15, 1%4, Ser. No. 375,043 7 illairns. (Cl. 117--97) ABSTRACT OF THE DISCLGSURE As one embodiment of the present invention, two spaced barrier members are adapted for sliding sealing engagement along the interior of a pipe, with the forward barrier member being coupled to a drag member by a tension member that is slidably received by the rearward barrier. To coat a pipe, a coating material is disposed between the barrier members and fluid pressure applied therebehind to propel the assembly along a pipe line. The drag member assures that the rearward barrier will gradually move forwardly along the tension member toward the forward barrier to displace coating material through suitable apertures in the forward barrier.

Accordingly, as will subsequently become more apparent, this invention relates to a method and apparatus for coating the interior of a pipe; and, more particularly, this invention pertains to a method and apparatus for placing a body of liquid in a pipe under pressure so that the liquid is squeezed into depression in the surface of the pipe.

Many devices have been proposed for applying an internal coating of treating material to a pipeline. However, none of these devices have been found effective to apply a thin, uniform coat of material around the entire periphery of a pipe. If pits or indentations exist in the line, as they frequently do in older pipelines, a method of treating the pipe, to be satisfactory, must also insure that these indentations or depressions in the pipe receive the coating of treating material.

It is therefore an object of the present invention to provide a method of and apparatus for applying a thin, uniform coating of material around the interior surface of a pipe.

Another object of this invention is to provide a method of and apparatus for coating the interior of a pipe in place utilizing swab members having a coating material placed between the members and arranged so that pressure is applied on the members to maintain the space between the members under pressure.

Still another object of the present invention is to provide a method of and apparatus for coating a pipe wherein the coating device is propelled through the line under gas pressure.

Still another object of the present invention is to provide a method of and apparatus for coating the interior surface of long sections of pipeline in place utilizing a moving chamber filled with a treating material wherein pressure is applied to the chamber by a gas used to propel the chamber through the pipe and a member dragged behind the propelled chamber.

With these and other objects in view, the present invention contemplates a method of and apparatus for applying coating material to the internal surface of a pipe in place. The pipe is opened at one end for the insertion of three pig or swab members in the pipe. These members are sized to provide a sliding fit within the pipe. A liquid treating material is placed in the space between the first and second swab members through a plug opening in the pipe. The third swab member is attached to the first swab member by means of a connecting mem- Lil 3,394fi25 Patented July 23, 1968 her which passes through an opening in the second swab member, the opening being sized to provide a sliding fit between the opening and the connecting member. A source of gas under pressure is then connected to the open or upstream end of the pipe. This gas under pressure passes through an opening in the third swab member to act upon the rear portion of the second swab member. The gas acting upon the second swab member forces the entire apparatus through the pipe. As the apparatus moves through the pipe, the liquid-filled chamber between the first and second members is constantly under pressure thereby forcing or applying the liquid about the internal surface of the pipe.

A complete understanding of this invention may be had by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 shows an elevational view in section of a pipeline with the apparatus embodying the present invention positioned therein; and

FIG. 2 is a cross-sectional view of the pipeline taken along lines 22 of FIG. 1.

Referring to FIGS. 1 and 2, a cut-away view of a pipeline 11 shows a lead pig or swab member 12 having a front 13 and rear 14 seal or cup connected by a shaft 16. The cups l3 and 14 may be made of neoprene or ther suitable material and have holes or lubricating ports 17a and 17 extending through the cups. An annular recess 15 is formed in the periphery of front cup 13 with the port 17a providing a passageway between the interior of the swab member 12 and the recess. A cable 18 is connected to the rear cup 14 of the lead pig and extends away from the lead pig and through a hollow shaft 21 connecting front and rear cups 22, 23 of a main pig 24. The cable, after passing through the main pig, then attaches to a drag pig 26. The drag pig likewise has front 27 and rear 28 seal members connected by a shaft 29, the shaft having a large axial opening 30 therethrough. The cups or swab members on the pigs are solid so as to prevent the bypass of gas or liquid around the cups. The hole extending through the shaft 21 of the main pig has a diameter just large enough to enable the main pig 24 to slide along the cable 18 but not large enough to permit the bypass of gas or liquid. The opening 30 in the shaft 29 extending through the drag pig 26 is large enough to permit sufficient gas flow through the pig so as not to apply an unequal force on the drag pig to cause independent motion of the drag pig.

A plug or access port 32 is provided in the pipe 11 to provide an opening through the pipe for the insertion of a liquid into a space 33 formed between the lead and main pig. A pressure regulator 34 is provided at the downstream end of the pipe 11 to maintain a proper differential of gas pressure at either end of the coating apparatus to control the speed of the apparatus through the pipeline. The upstream or open end 35 of the pipe is connected to a supply of gas under pressure (not shown).

In the operation of the apparatus set forth above, the three pig members 12, 24 and 26 are placed in the line as illustrated in the drawing with the lead pig 12 and main pig 2 E- sufiiciently spaced to provide a chamber 33 therebetween for holding a coating agent in sufficient quantity to ensure the proper coating of the entire length of line to be treated. Subsequent to placing the members in the line, the drag member 26, positioned behind the lead and main pigs, is connected to the lead pig by the cable 18. Next, the treating liquid is inserted into the chamber 33 between the first and second pig members through the access port 32. This liquid also passes through the ports 17 to fill the interior of the lead swab member 12. Gas pressure is then suplied to the upstream or open endv 35 of the pipe, which gas pressure is applied to the 3 rear cup 23 of the main pig 24 through the opening 30 in the drag pig shaft 29. This gas pressure tends to force the main pig 24 forward in the direction of the arrow 'toward the lead pig 12 thereby pressuring the coating agent spaced therebetween in chamber 33 and also between cups 13 and 14 of the lead pig to ensure that the coating agent is in contact with the entire peripheral wall of the pipe interior. The force of the gas acting on the rear cup of the main pig 24 is transmitted through the incompressible liquid coating agent to the lead pig 12 thereby propelling the lead pig and thus the entire appara tus through the pipe. The cable 18 extending from the lead pig 12 and connected to the drag pig 26 provides a dragging force on the lead pig to act against the gas propelling force thereby ensuring that the space 33 between the lead and main pigs is subjected to a pressure at all times. This pressure is substantially equal to the pressure caused by drag on the lead pig plus the pressure of the line in front of the lead pig.

Lubricating ports 17a are formed in the front cup member 13 of the lead pig 12 to provide for a leakage or spray of the coating agent through the ports onto the pipe surface in front of the lead pig. This leakage of fluid in front of the lead pig 12 provides for the lubrication of the pipe surface directly in front of the lead pig.

As the pigs move along the pipeline, the coating agent in the chamber 33 and within the lead pig 12 is spread evenly along the internal pipe surface. As the coating agent is dispersed onto the pipe, the main pig 24 moves along the cable 18 in the manner of a piston toward the lead pig 12 to maintain pressure on the coating agent in the space 33 between the main pig and the lead pig. The cups of the main pig 24 and the drag pig 26 act to spread the coating agent evenly along the internal pipe surface. The pressure regulator 34 which is installed on the discharge end of the line is used to maintain a proper differential of gas pressure in front of the pig assembly. Therefore, by regulating the input of gas behind the apparatus and the downstream pressure in front of the apparatus, the coating device may be moved through the pipe at any desired speed depending upon the amount and characteristics of coating material to be applied to the pipe.

It will be appreciated that other methods of propelling the apparatus through the pipe might be used which would encompass the advantages of the present invention.

Additionally, while a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made Without departing from this invention in its broader aspects and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is: 1. A method for treating the internal surface of a pipe in place comprising the steps of:

maintaining a treating material between spaced first and second sliding members positioned with a pipe;

attaching a third sliding member, positioned behind the first and second sliding members, to the first sliding member;

passing a gas under pressure through the third sliding member to act on the second sliding member in a direction tending to move the second sliding member toward the first sliding member to thereby move both the first and second sliding members through the pipe and at the same time drag the third sliding member behind the first and second sliding members; and

passing a portion of the treating material, maintained between the first and second sliding members, through openings in the first sliding member onto the pipe in front of the sliding members as they are moved through the pipe,

2. The method of claim 1 further comprising the step regulating the pressure in the pipe in front of the sliding members moving through the pipe to thereby regulate the speed of the sliding members through the pipe. 3. Apparatus for coating the interior of a pipe comprising:

forward and intermediate members having swab portions for contacting the wall of a pipe and arranged to confine a liquid coating material therebetween, a drag member to the rear of said forward and intermediate members, and means directly coupling said forward and drag members to one another, said intermediate member being movable relative to said coupling means and forward and drag members, said drag member having an opening to permit application of pressure to said intermediate member and said forward member having at least one discharge opening therein to permit a liquid coating to be displaced from between said forward and intermediate members onto the wall of a pipe ahead of said apparatus. 4. An apparatus for treating the internal surface of a pipe comprising:

first and second spaced members having swab portions adapted for slidably engaging the wall of a pipe and spaced apart from one another; discharge means in said first member adapted for discharging fluid materials confined between said spaced members onto pipe surfaces ahead of said apparatus; and a drag member having a swab portion positioned on the side of said second member opposite said first member and attached to said first member, said drag member having an opening to permit application of pressure to said second member. 5. An apparatus for coating the internal surface of a pipe comprising:

first and second means spaced apart and having swab portions adapted for slidably engaging the wall of a pipe, said first means being spaced from said second means and adapted for confining a coating liquid therebetween, discharge means in said first means adapted for discharging coating liquids confined between said spaced means onto pipe surfaces ahead of said apparatus, and drag means attached to said first means and adapted for being positioned in a pipe on the other side of said second means, said drag means having portions forming a sliding frictional fit within such a pipe, said drag means further having an opening therethrough for permitting the passage of a gas from one side of said drag means to the other so that gas may be applied to the other side of said second sliding swab means to move said apparatus through a pipe. 6. An apparatus for coating the internal surface of a 60 pipe comprising:

first and second means having swab portions adapted for slidably engaging the internal wall of a pipe, said first means being spaced from said second means and adapted for confining a coating liquid therebetween, and drag means attached to said first means and adapted for being positioned in a pipe on the other side of said second means, said drag means having swab portions forming a sliding fit within such a pipe, said drag means further having an opening therethrough for permitting the passage of a gas across said drag means for applying gas pressure to the other side of said second sliding swab means to move said apparatus through a pipe,

port means in said first sliding swab means providing for the flow of treating material into a pipe in front of the apparatus moving through a pipe.

7. Apparatus for coating the interior of a pipe comprising:

forward, intermediate and rearward members, each of said members having cup portions thereon adapted for contacting the wall of a pipe, and

a cable connecting the forward and rearward members,

said intermediate member having an opening therethrough for slidably receiving said cable therein so that said intermediate member is free to move along said cable relative to said forward and rearward members,

said rearward member having an opening for permitting the passage of gas pressure through said rearward member to be applied to said intermediate member, and said forward member having a plurality of openings therein adapted for discharging coating materials confined between said forward and intermediate members onto the internal surfaces of a pipe ahead of said forward member.

References Cited UNITED STATES PATENTS 2,480,358 8/ 1949 Curtis et a1. 2,808,852 10/ 1957 Brant 118408 3,041,204 6/1962 Green 118-105 3,125,464 3/ 1964 Harmes.

FOREIGN PATENTS 685,407 4/1964 Canada.

ALFRED L. LEAVITT, Primary Examiner. A. M. GRIMALDI, Assistant Examiner. 

